Typically, a seismic data acquisition system comprises a network connected to a central unit. The central unit collects the seismic data and processes them to generate a specific file (SEGD) analysed by the seismic community.
In a first known implementation (also referred to below as “wired implementation”), the network comprises a plurality of wired acquisition lines. Each wired acquisition line comprises nodes (also referred to as “seismic acquisition units”) and concentrators, thus all data can be received in the central unit in a real-time manner. The nodes are assembled in series along a telemetry cable and are each associated with at least one seismic sensor (in general, strings of seismic sensors). These nodes process signals transmitted by the seismic sensor(s) and generate data. The data include seismic data and non-seismic data. The non-seismic data are for example QC data (for “Quality Control data”), i.e. information concerning the health of the node (such as battery level, synchronisation availability, sensor status, memory status, etc.). The concentrators are assembled in series along the telemetry cable and are each associated with at least one of the nodes. Each concentrator receives the data generated by the node(s) with which it is associated. The sensors are either analog sensors or digital sensors. When analog sensors (also referred to as “geophones”) are used, they are generally interconnected by cables to form clusters referred to as “strings of geophones”. One or several of these strings of geophones (in series or in parallel) are connected to each node and this latter performs an analog to digital conversion of the signal from the groups of geophones and send these data to the central unit (via the network of concentrators). When digital sensors are used (e.g. micro-machined accelerometers, also referred to as “MEMS-based digital accelerometer”), they are integrated in the nodes, thus eliminating the geophone strings. Each node integrates one or several digital sensors.
In a second known implementation (also referred to below as “wireless implementation”), the network comprises wireless seismic acquisition units. Each wireless seismic acquisition unit (also called “node”) is independent and associated with (i.e. is connected to or integrates one or several functions of) one or several of aforesaid nodes and generates data (including seismic data and non-seismic data).
In the wireless implementation, different kinds of networks have been proposed to collect (i.e. harvest) the data from the wireless seismic acquisition units to the central unit:                a) wireless point-to-multipoint network (WIFI for example), as shown in the example of FIG. 1:                    i. the central unit CU acts as a central point of a first wireless point-to-multipoint network and receives data (seismic data (noted “DATA”) and non-seismic data (noted “QC”)) from wireless seismic acquisition units 2 located in a coverage area 3 of the central unit;            ii. if a “on the ground” data harvesting is implemented, each data harvester equipment DH (carried by an operator of a field team, also referred to as “harvester”) acts as a central point of a second wireless point-to-multipoint network and receives data (seismic data (noted “DATA”) and non-seismic data (noted “QC”)) from wireless seismic acquisition units 2 located in a coverage area 5 of the harvester equipment;                        b) wireless cellular network: the wireless seismic acquisition units behave as mobile stations of the wireless cellular network, and can send data (seismic data and non-seismic data) to the central unit, via the infrastructure of the wireless cellular network; and        c) wireless multi-hop network, as disclosed in U.S. Pat. No. 8,238,197B2 and shown in the example of FIG. 2: wireless seismic acquisition units 2 and base stations 7 are nodes of a wireless multi-hop network (i.e. they are configured to communicate with surrounding nodes through wireless links). Seismic data (noted “DATA”) are forwarded by the wireless seismic acquisition units 2 until they reach one of the base stations 7. In other words, each wireless seismic acquisition unit 2 send its seismic data to a base station 7 via a multi-hop path comprising a sequence of wireless seismic acquisition units. Each base station 7 is capable of transferring the received seismic data to a central unit CU (also referred to as “central control and recording system”) by any suitable method (e.g. Ethernet, USB, fiber-optic link, wireless interface such as IEEE 802.11, etc.). U.S. Pat. No. 8,238,197B2 is silent about the transmission of the non-seismic data (e.g. QC data).        
The wired implementation and the wireless implementation (whatever the kind of network used) have drawbacks discussed below.
Currently, in the wired implementation, the paths from the nodes to the central unit (i.e. seismic acquisition unit) are the same for the seismic data and the non-seismic data (e.g. QC data). That means that the non-seismic data are collected by the central unit which also collects and processes the seismic data. In other words, all the information is centralized in the central unit. A drawback is that the field team shall always communicate with the lab team that manages the central unit in order to obtain information (e.g. non-seismic data, but possibly also seismic data) concerning the seismic acquisition units deployed on the field. In other words, a field operator (of the field team) is not able to retrieve and process the non-seismic data coming from the seismic acquisition units, without any communication with the lab team. Thus, the field operator is not autonomous to manage the seismic acquisition units on the field.
Currently, when a wireless point-to-multipoint network is used in the wireless implementation, with the central unit (CU) acting as a central point (above case a-i and left side of FIG. 1), a drawback is that only wireless seismic acquisition units located in the coverage area of the central unit can access the wireless point-to-multipoint network and send their data to the central unit. Another drawback is that the field team has to communicate with the lab team (that manages the central unit) in order to obtain information (e.g. non-seismic data, but possibly also seismic data) concerning the wireless seismic acquisition units deployed on the field. Therefore, as for the wired implementation, the field operator is not able to retrieve and process the non-seismic data coming from the seismic acquisition units, without any communication with the lab team.
Currently, when a wireless point-to-multipoint network is used in the wireless implementation, with the harvester equipment (DH) acting as a central point (above case a-ii and right side of FIG. 1), the field team can directly collect seismic data and non-seismic data on the field. This case makes the field team more autonomous. However, it has other drawbacks: the wireless seismic acquisition units shall be configured (e.g. IP address or WIFI parameters or any network configuration parameters) in order to communicate with the harvester equipment; only wireless seismic acquisition units located in the coverage area of the harvester equipment can access the wireless point-to-multipoint network and send their data to the harvester equipment; the number of wireless seismic acquisition units that the harvester equipment can manage on the field is limited (e.g. one dozen); and the wireless seismic acquisition units located in harsh environment (forest, dense vegetation, etc.) are not accessible by the harvester equipment (i.e. all of them cannot be reached by the harvester equipment).
Currently, when a wireless cellular network is used in the wireless implementation (above case b), a main drawback is that a heavy infrastructure must be deployed on tens of km2 areas to harvest all the data in real time. Moreover, the field team has to communicate with the lab team (that manages the central unit) in order to obtain information (e.g. non-seismic data, but possibly also seismic data) concerning the wireless seismic acquisition units deployed on the field. Therefore, as for the wired implementation, the field operator is not able to retrieve and process the non-seismic data coming from the seismic acquisition units, without any communication with the lab team.
Currently, when a wireless multi-hop network is used in the wireless implementation (above case c), as disclosed in U.S. Pat. No. 8,238,197B2, a real time harvesting of the seismic data (DATA), by the central unit, is possible only for a limited number of wireless seismic acquisition units because of the limited bandwidth of such networks and wireless seismic acquisition units suffer from high power consumption. The number of wireless seismic acquisition units deployed on the field is thus limited. Moreover, as this is a centralized configuration, the field team has to communicate with the lab team (that manages the central unit) in order to obtain information concerning the wireless seismic acquisition units deployed on the field. Therefore, even if we assume that the technique of U.S. Pat. No. 8,238,197B2 is used to transmit the non-seismic data (e.g. QC data) together with the seismic data (DATA), the field operator is not able to retrieve and process these non-seismic data coming from the seismic acquisition units, without any communication with the lab team.